I. Field
The present disclosure relates generally to communication, and more specifically to acquisition techniques for a communication system.
II. Background
Orthogonal frequency division multiplexing (OFDM) is a multi-carrier modulation technique that can provide good performance for some wireless environments. OFDM partitions the overall system bandwidth into multiple (K) orthogonal frequency subbands, which are also called carriers, subcarriers, tones, and so on. With OFDM, each subband is associated with a respective carrier that may be modulated with data.
In an OFDM system, a transmitter processes (e.g., encodes, interleaves, and modulates) traffic data to generate modulation symbols and further maps the modulation symbols to the K subbands. The transmitter then transforms the modulation symbols to the time domain and generates OFDM symbols. Each OFDM symbol contains a useful part and a guard interval, which is a repeated portion of the useful part. The OFDM system may support different modes for different values of K and different guard lengths for different guard interval durations. The transmitter would then generate the OFDM symbols in accordance with the mode and guard length selected for use. The transmitter transmits the OFDM symbols to receivers.
A receiver performs the complementary processing on the OFDM symbols received from the transmitter. The receiver typically first detects the mode and guard length used by the transmitter. The receiver then processes each received OFDM symbol in accordance with the detected mode and guard length. It is desirable to quickly and reliably detect the mode and guard length so that the processing of the received OFDM symbols can commence as soon as possible.
There is therefore a need in the art for techniques to detect mode and guard length in an OFDM system.